<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>自定义下拉菜单</title>
</head>
<style>
    [v-cloak] {
        display: none;
    }

    .main {
        width: 125px;
    }

    button {
        display: block;
        width: 100%;
        color: #fff;
        background-color: #39f;
        border: 0;
        padding: 6px;
        text-align: center;
        font-size: 12px;
        border-radius: 4px;
        cursor: pointer;
        outline: none;
        position: relative;
    }

    button:active {
        top: 1px;
        left: 1px;
    }

    .dropdown {
        width: 100%;
        height: 150px;
        margin: 5px 0;
        font-size: 12px;
        background-color: #fff;
        border-radius: 4px;
        box-shadow: 0 1px 6px rgba(0, 0, 0, 0.2);
    }

    .dropdown p {
        display: inline-block;
        padding: 6px;
    }
</style>
<body>
<div id="app" v-cloak>
    <div class="main" v-clickoutside="handleClose">
        <button @click="show = !show">点击显示下拉菜单</button>
        <div class="dropdown" v-show="show">
            <p>下拉框的内容,点击外部可以关闭</p>
        </div>
    </div>
</div>
</body>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
    Vue.directive('clickoutside', {
        bind: function (el, binding, vnode) {
            function docHandler(e) {
                if (el.contains(e.target)) {
                    return false;
                }
                if (binding.expression) {
                    binding.value(e);
                }
            }

            document.addEventListener('click', docHandler);
        },
        unbind: function (el, binding) {
            document.removeEventListener('click', el.__vueClickOutside__);
            delete el.__vueClickOutside__;
        }
    })
    var app = new Vue({
        el: '#app',
        data: {
            show: false
        },
        methods: {
            handleClose: function () {
                this.show = false;
            }
        }
    })
</script>
</html>
